Tuberculosis can remain latent for decades, and billions of people worldwide are infected, yet this is the stage of the disease about which the least is known. There has been an explosion of research data about the state of dormancy of the mycobacterial pathogen and the adaption of the pathogen to residence in the host, both at the level of gene expression and protein expression. At the same time very little is known about host immune reactions during the period of latency, especially those reactions which are localized in the granulomatous inflammatory lesions. The hard walled granuloma acts to prevent the dissemination of the pathogen and also protects the surrounding host tissue. The extent to which it also shields the bacteria from sterilizing immunity and possibly prevents access of the immune system to the pathogen is unknown. There is an urgent need for information about the specific immune response against dormant mycobacteria. In particular, little to no information is available about the extent to which host dendritic cells (DC) are able to sample antigens exclusively expressed by dormant, granuloma dwelling bacteria. Similarly, the systemic response of T cells to latency antigens has not been widely characterized. We will induce granulomas in murine liver using a Mycobacterium bovis strain bacille Calmette Guirin (BCG) infection model. Liver pieces containing granulomas will be transplanted into mice at the chronic stage. By taking advantage of fluorescence-tagged DC, T cells and bacteria localized in chronic granulomas, we will trace their traffic from the transplant. By using combinations of genetically epitope-tagged BCG and T cell receptor transgenic mice we will also test the capacity of donor-derived DC to present latent mycobacterial antigens and the systemic response of T cells to latent mycobacterial antigens. PUBLIC HEALTH RELEVENCE:Our experiments will ask the key question of whether during chronic mycobacterial infection, the granuloma sequestered bacteria are able to induce a systemic host immune response or not. The potential answers from these experiments could be critically important to the tuberculosis vaccine effort. These experiments will increase our understanding of other infectious and autoimmune granulomatous diseases and their long- term immunopathologies.